Roundworms on the Red Island: Gastrointestinal parasite intensity in four lemur species from the Tsinjoarivo region, Madagascar

The lemurs of Madagascar are hosts to a number of infectious agents, including many taxon-specific gastrointestinal parasites. Parasite loads affect individual fitness, social systems, and behavior; their consideration is therefore vital to conservation planning. The Tsinjoarivo region of Madagascar’s central high plateau contains nine species of lemurs, all of which are threatened by anthropogenic forest fragmentation. This makes it an ideal location to study effects of fragmentation on lemur parasitic loads.

In this study, we used fecal flotations to analyze parasite intensity in four species of lemurs (Hapalemur griseus, Propithecus diadema, Microcebus murinus, and Avahi laniger) and four species of domestic animals (Canis familiaris, Bos indicus, Sus scrofa, and Oryctolagus cuniculus) in the Tsinjoarivo region. Parasite eggs and larvae were counted and photographed within 24 hours of fecal collection. Collection priority was given to fecal samples from H. griseus and P. diadema. The most common parasites across all species were nematodes of the family Strongylidae. Subject species had low levels of parasite intensity (0-50 eggs/larvae), with the exception of H. griseus, which consistently maintained the highest parasite intensity and diversity. Three hypotheses explaining higher parasite loads in H. griseus include 1) increased exposure to parasites due to lower preferred canopy height, 2) grooming behavior that does not adequately target strongyles, and 3) overcrowding effects from landscape fragmentation, which preferentially affect H. griseus due to their reliance on bamboo commonly found along fragment edges. Data regarding the behavior of H. griseus and strongyle lifecycles provide support for the fragmentation hypothesis.